A conventional halogen lamp light source has been replaced with an LED (light emitting diode) illumination light source as illumination light of a microscope for the following reasons. That is, since a halogen lamp largely changes its color temperature (chromaticity) by light control, it is necessary to provide an optical element such as a darkening filter etc. for light control without changing the chromaticity. On the other hand, an LED can perform the light control only by changing a voltage and a current almost without changing the chromaticity. Therefore, when an LED is used as a light source, it has the merit of requiring no additional configuration. With predetermined quantity of light, an LED requires much less power consumption than a halogen lamp. Accordingly, when an LED is used as a light source, it has the merit of reducing excess power or heat.
As the background of replacing the conventional illumination light source, the emission efficiency of an LED has made rapid improvement, and has realized the luminance that can be used for a microscope.